Compression coding techniques are often used when transmitting a speech/sound signal in a packet communication system represented by Internet communication or a mobile communication system or the like, to improve transmission efficiency of the speech/sound signal. In addition to simply encoding the speech/sound signal at a low bit rate, there is also a growing demand for a technique for encoding a wider band speech/sound signal and a technique for encoding/decoding with a low amount of processing calculation without causing degradation of sound quality.
Various techniques for satisfying such a demand are being developed to reduce the amount of processing calculation without causing quality degradation of a decoded signal. For example, according to a technique disclosed in Patent Literature (hereinafter, abbreviated as PTL) 1, a CELP (Code Excited Linear Prediction) type coding apparatus calculates energy of an inputted speech signal before a linear predictive analysis. According to PTL 1, a linear predictive analysis is performed only when the calculated energy is determined not to be 0, whereas a linear prediction coefficient according to a predetermined fixed pattern is outputted when the calculated energy is determined to be 0. This scheme can cut down on waste of performing a time-consuming linear predictive analysis and thereby shorten the processing time and also suppress current consumption accompanying the amount of processing calculation.